Hydrogel Membrane for Adhesion Prevention

ABSTRACT

A biocompatible membrane comprised of alginate and hyaluronate. The membrane may be used to prevent unwanted scarring after surgery. The tissue adherence and the rate of bioresorption of the membrane may be modified through an external stimulus comprising a sequestering agent and a viscosity modifier.

This application is a continuation of U.S. patent application Ser. No.14/758,873, filed Jul. 1, 2015, which is a §371 National Stage Entry ofInternational Application No. PCT/US2013/074388 filed on Dec. 11, 2013,which claims priority to: (1) U.S. Provisional Application No.61/814,944 filed on Apr. 23, 2013, (2) U.S. Provisional Application No.61/807,629 filed on Apr. 2, 2013, and (3) U.S. Provisional ApplicationNo. 61/735,852 filed on Dec. 11, 2012. The content of each of the aboveapplications is hereby incorporated by reference.

This invention was made with government support under Grant no.DMR0805298 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

FIELD OF EMBODIMENTS OF THE INVENTION

Embodiments of the invention relate generally to the field of medicaldevices and more particularly to devices that inhibit, reduce, andprevent scarring. Embodiments of the invention include a bioresorbablemembrane that can be inserted into the body, between tissues and organs,to prevent unwanted scar tissue attachments.

BACKGROUND

Scar tissue attachments, also called adhesions, are a frequentcomplication of surgical procedures. During a surgical procedure thetissues and organs of the body may be deliberately or inadvertentlyinjured. These injuries prompt a wound healing response that results inscarring.

Scarring is problematic when it produces scar tissue attachments betweenadjacent tissues and organs that should remain unattached. Adhesions arecapable of forming in any anatomical location including around the eyes,tendons, heart, spinal cord, peripheral nerve, sinus, and among theorgans of the abdominal and pelvic cavities. For example, a bowelresection within the abdominal cavity may lead to scar tissueattachments between the bowels and the abdominal wall. These attachmentscan produce pain and discomfort for the patient, impair the functioningof the effected organs, and hinder subsequent surgeries in the sameanatomical region.

An anti-adhesion barrier is a medical device used by surgeons toinhibit, reduce, or prevent scar tissue attachments. These devices arecommercially available as membranes, gels, and solutions. During asurgical procedure a surgeon may choose to insert an anti-adhesionbarrier between injured tissues and organs. Such devices work byphysically separating the injured organs during the critical period ofwound healing during which patients are most at risk for adhesions.After the critical phase has passed the devices are resorbed by thebody. Generally, membrane barriers are superior to gels and solutionswhich are resorbed by the body too quickly. Even the most successfulmembranes, however, are only partially effective and may suffer frombrittleness and poor resorbability.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the present invention willbecome apparent from the appended claims, the following detaileddescription of one or more example embodiments, and the correspondingfigures, in which:

FIG. 1 includes a photo of a hydrogel in an embodiment of the invention.

FIG. 2 includes a chart regarding swelling of a hydrogel in anembodiment of the invention.

FIG. 3 includes a series of photos illustrating mucoadhesiveness of anembodiment of the invention.

FIG. 4 addresses a bilayer hydrogel in an embodiment of the invention.

FIG. 5 includes a process for making a bilayer hydrogel in an embodimentof the invention.

FIG. 6 includes a method 600 in an embodiment of the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forthbut embodiments of the invention may be practiced without these specificdetails. Well-known circuits, structures and techniques have not beenshown in detail to avoid obscuring an understanding of this description.“An embodiment”, “various embodiments” and the like indicateembodiment(s) so described may include particular features, structures,or characteristics, but not every embodiment necessarily includes theparticular features, structures, or characteristics. Some embodimentsmay have some, all, or none of the features described for otherembodiments. “First”, “second”, “third” and the like describe a commonobject and indicate different instances of like objects are beingreferred to. Such adjectives do not imply objects so described must bein a given sequence, either temporally, spatially, in ranking, or in anyother manner. “Connected” may indicate elements are in direct physicalor electrical contact with each other and “coupled” may indicateelements co-operate or interact with each other, but they may or may notbe in direct physical or electrical contact.

Clinicians are seeking anti-adhesion membranes with improved handlingproperties and greater efficacy. As discussed below, various embodimentsof the invention provide a membrane that is hydrated, resorbable, andeffective.

An embodiment includes a membrane comprised of two polysaccharides:alginate and hyaluronate. An embodiment may include a membrane includingonly alginate and hyaluronate and little to nothing else. Theproportions of each polymer within the membrane may vary with differentembodiments For example, in one embodiment the alginate component mayconstitute up to 95%, and no less than 10%, of the dry mass (withhyaluronate constituting the remaining portion of the film). In anotherembodiment the membranes comprise no more than 75% and no less than 50%alginate by dry weight (with hyaluronate constituting the remainingportion of the film). In an embodiment the membranes comprise between60% and 70% alginate (with hyaluronate constituting the remainingportion of the film).

In an embodiment the alginate component may be a copolymer ofmannuronate (M) units and guluronate (G) chemical units. The alginatebackbone may consist of these two units arranged in repeating blocks andalternating blocks (e.g., MMMMMM, GGGGGG, and MGMGMG patterns). Theproportion of M and G units in a particular alginate is dependent on,for example, the plant source from which the alginate is harvested insome embodiments. Alginates may be characterized by the proportion of Mand G units. The alginate component in an embodiment may be any type ofalginate including alginates with a high proportion of M units (i.e.,high-M alginate), alginates with a high proportion of G units (i.e.,high-G alginate) and blends of high-M and high-G alginates. In anembodiment a “high proportion” of a unit constitutes more than 50% butin other embodiments the value may be 60%, 70%, 80%, 90%, or higher.

Alginates may be obtained in a variety of salt forms. The alginate saltsof alkali metals (e.g., sodium and potassium) and magnesium are watersoluble. The alginate salts of alkaline earth metals (e.g., calcium,strontium, barium) are water insoluble. Alginate can also form insolublesalts with transition metals such as iron and copper. The waterinsolubility of alginate salts may be due to ionic crosslinking bymultivalent cations of the G-units in alginate's backbone. In anembodiment a water soluble alginate is used to prepare solutions forfilm casting. After casting the alginate is converted to an insolublesalt form by ion exchange to obtain the final membrane. In an embodimentsodium alginate is used for film casting and subsequently converted tocalcium alginate after the membrane has been obtained. Calcium, anelement found throughout the body, may serve as a crosslinker and is asuitable option from the point of view of biocompatibility.

Hyaluronate is an alternating polysaccharide of N-acetylglucosamine andglucuronic acid chemical units. The polymer can be obtained from, invarious embodiments, both animal and bacterial sources and in a numberof molecular weights. An acid form, hyaluronic acid (HA), can beobtained but has limited water solubility. Hyaluronate stocks forresearch and clinical use are predominantly salts, particularly sodiumsalts. In an embodiment sodium hyaluronate salt is used for membranepreparation due to, for example, its commercial availability. Othersalts can also be obtained, but unlike alginate, these salts are watersoluble.

Hyaluronate is found throughout the connective tissues of the bodyparticularly in the skin, cartilage, and vitreous fluid of the eye. Itis an unusually large macromolecule that can reach molecular weights ofup to several million. It is capable of binding to specialized proteinsto form macromolecular complexes that are structural frameworks fortissue development and wound healing. The backbone of hyaluronate ishighly negatively charged due to the prevalence of carboxylfunctionalities. Hyaluronate is unique in the body due to thecombination of high molecular weight and high charge density. Theseproperties may make hyaluronate capable of binding to many watermolecules thereby helping tissues to maintain hydration and homeostasis.

Hyaluronate is biocompatible. Hyaluronate is nearly ubiquitousthroughout the tissues of the body; therefore, the immune system doesnot recognize it as foreign. Additionally, hyaluronate is stronglyassociated with wound healing and particularly with scar-free woundhealing and fetal tissue development.

HA may be crosslinked. Methacrylate groups are bound to an availablecarboxylic acid group and these groups then bind together viaphotocuring. However, photocrosslinked HA alone renders films that maynot be robust, may tear easily, and may be difficult to handle. In orderto obtain films that have more structure and strength, an embodimentadds alginate. Calcium is used as a crosslinker because it isbiocompatible and the body has systems in place to regulate calciumlevels.

More specifically, an embodiment includes a membrane comprised of bothhyaluronate and alginate. In addition to these polymers the membranesmay also contain a significant proportion of water and can be classifiedas hydrogels. Hydrogels are materials that swell when exposed to excesswater. At a molecular level hydrogels are comprised of a network ofpolymer chains that are dispersed within an aqueous medium. A feature ofthe hydrogel membranes of an embodiment is the crosslinks that tietogether the individual polymer chains. These crosslinks allow thehydrogel to swell in water but prevent it from completely dissolving.Hydrogels tend to be biocompatible because water itself isbiocompatible. Hydrogels therefore are attractive for clinicalapplications in which materials will come into close contact with livingtissues.

In an embodiment alginate forms the framework of the membrane due to itsability to create crosslinked gels in the presence of calcium. Thiscrosslinked framework provides mechanical stability and shape to themembrane. The hyaluronate component is entrapped within the alginate geland its release is limited by its large size compared to the pores ofthe alginate gel. Hyaluronate is more hydrophilic than alginate andtherefore hydrogel compositions with greater proportions of hyaluronateexhibit greater water swelling. When the ratio of hyaluronate toalginate is low the hyaluronate component is entirely or partiallyentrapped within the crosslinked alginate matrix and leaching islimited; but when the ratio of hyaluronate to alginate is high, thecrosslinked alginate may be unable to retain the leachable hyaluronatecomponent. The hyaluronate component can be leached by rinsing themembrane in water for which hyaluronate has a strong affinity. Whenhyaluronate is leached it leaves behind empty pores within the membranethat provide an interconnected pathway for diffusion of water. Byaltering the pores, and therefore the water content of the membrane, thephysical properties of the membrane such as flexibility and elasticityare also altered. The leaching of hyaluronate from the membrane duringmanufacturing may be used as a means to advantageously modify thephysical properties of the membrane. The leaching of hyaluronate mayalso occur in vivo as a means to deliver hyaluronate to a wound site tocapitalize on hyaluronate's pro-regenerative wound healing properties.

FIG. 2 shows the water swelling ratio of alginate/hyaluronate membranesas a function of composition. The membranes are hydrophilic and absorbwater. Increasing the proportion of hyaluronate within the membranesrenders them more hydrophilic and increases their water swellingcapacity.

In an embodiment membranes are prepared through solution casting. Thisrequires dissolving water soluble salt forms of the alginate andhyaluronate in an aqueous mixture. Then a volume of the solution can bedispensed into a mold. A suitable mold can be of any shape or size. Thewater from the solution may be evaporated to obtain a dry thin filmwhich can be crosslinked by a soak in an aqueous solution of a calciumsalt. Crosslinking produces a hydrogel membrane that swells in water butdoes not dissolve. Similar techniques for obtaining cast films such asspin-casting, doctor-blading with a casting knife, extrusion and thelike can produce films without the need for a water evaporation step.These films can be crosslinked with calcium without the need for drying.

A doctor blade is a tool used to create wet films with a definedthickness. To use the doctor blade in an embodiment one dispenses avolume of alginate/hyaluronate solution onto a substrate. Then one pullsthe doctor blade over the solution to spread it into a flat film ofdefined thickness. The doctor blade removes excess solution therebyproducing a wet film of predefined thickness coating the substrate.

Tissue Anchor

Discussion now turns more specifically to an embodiment for a liquidtissue anchor with a sequestering solution. Embodiments of the tissueanchor described below may be used with embodiments discussed above ormay be used independently of those embodiments.

An embodiment includes a method of treating an adhesion barrier, or anyimplantable device, comprised of crosslinked constituents (such ascalcium alginate) that can be uncrosslinked by removing one or morecrosslinking agents (such as calcium), with a sequestering solution thatremoves the crosslinking agent(s) (such as calcium) at the site ofinjury. An embodiment of the invention can also be understood as thesequestering solution itself (independently of the implant).

One embodiment of a sequestering solution includes a calcium chelator,but other embodiments are not so limited.

In an embodiment the sequestering solution works by disrupting thecrosslinks (see discussion above regarding crosslinking embodiments)within the implant. Disruption of the crosslinks occurs by bonding ofthe sequestering agent to the crosslinking agent within the implant. Fordisruption to occur, in one embodiment the sequestering agent bonds morestrongly to the crosslinking agent than does the crosslinkable componentof the implant. More specifically, a sequestering agent is able tosequester the crosslinking agent or ion because by doing so, the overallenergy of the system is lowered. This energy lowering causes arelaxation of the implanted device, reducing the mechanical integrity ofthe device. The device conforms to the tissue geometry, and becomesmucoadhesive by nature of hydrogen bonding. This mucoadhesivity removesthe need for other anchoring devices such as sutures or tissue glue.

FIG. 3 is a sequence of photos depicting the application of a membraneof alginate and hyaluronate to the intestine of a rat model of abdominalinjury. The membrane is flexible and easy to position at the correctsite. The syringe applies an optional liquid tissue anchor that promotestissue adherence and bioresorption of the membrane.

Mechanically robust implants (such as an alginate adhesion membrane) maypersist inside the body beyond the critical healing period (about twoweeks), which may be problematic because the odds of an undesirableimmune response are greater if the implant persists within the body fora long period of time. However, in an embodiment the sequesteringsolution increases the rate of bioresorption of the adhesion barrier. Inan embodiment the implanted device completely resorbs within two weekspostsurgically, based on its use with the sequestering solution.However, other embodiments may shorten or lengthen this period of time.

In various embodiments suitable sequestering agents are salts of organicmolecules that have multiple anionic functional groups capable ofbonding to a crosslinking agent (such as calcium, magnesium, cadmium,silver, zinc, silicon, oxidants, protic acids, compounds that can bemetallated). Examples are the salts of citric acid, EDTA, EGTA, BAPTA,tetracycline, and phosphates.

In an embodiment the strength of the sequestering solution is dependenton the molar concentration of the sequestering agent. For example, asolution formulated with a greater molar concentration of sequesteringagent disrupts a greater number of crosslinks within the implant andaccordingly increases the rate of bioresorption. Therefore, theconcentration of the sequestering agent within the sequestering solutioncan be tuned to obtain a desired rate of implant resorption within thebody. For example, 300 mM citrate yields a 1 week bioresorption of analginate/hyaluronate film crosslinked with 100 mM calcium chloridesolution. Meanwhile 100 mM citrate yields a 2 week bioresorption of analginate/hyaluronate film crosslinked with 100 mM calcium chloridesolution. Furthermore, without use of the sequestering solution, thissame film persists for 6 weeks. This tunability allows for one implantto facilitate healing support for various indications. For example,hernia repair may require longer time periods of support untilfibroblast ingrowth is sufficient, like 6 weeks. This timeframe isopposed to abdominal adhesion prevention which requires bioresorption inabout 2 weeks.

In an embodiment a surgeon uses the sequestering solution during anysurgical procedure in which an implant, comprised of crosslinkedconstituents (such as calcium alginate) that can be uncrosslinked withthe sequestering solution, is used to prevent unwanted tissue adhesionsor unwanted scar tissue attachments. The surgeon applies thesequestering solution by a suitable delivery device (e.g., syringe,spray, and the like) to the surface of the implant. The sequesteringsolution acts quickly to disrupt the unwanted crosslinks (such ascalcium). The treated implant then conforms to and adheres more stronglyto the contours of the underlying tissues.

To facilitate application of the sequestering solution to the injurysite, in an embodiment the sequestering solution may be formulated witha thickening agent. The thickening agent increases the solutionviscosity to produce a thick, syrupy liquid. A beneficial effect of thethickening agent is that the more viscous sequestering solution isbetter confined to the site of application than is a less viscous waterysolution. An embodiment includes a thickening agent such as sodiumhyaluronate, which is known for both its biocompatibility and solutionthickening properties.

In the interests of biocompatibility in various embodiments thesequestering solution can be formulated with salts to buffer the pH oradjust the osmolarity such as those found in commonly used phosphatebuffer solution.

An embodiment includes an alginate barrier crosslinked specifically withcalcium and treated with a corresponding calcium sequestering solution.However, in other embodiments the same method can be applied to otherions as well. For example, in various embodiments alginate barriers arecrosslinked with cations such as barium, strontium, copper, iron, andthe like. The same sequestering agents may be used to disrupt thesecrosslinking agents.

Crosslinking of materials includes an increase in the number of bondsbetween a material and itself or other materials. An increase in bondscauses a change in the refractive index of the overall material,distorting light going through the material. As the embodiment includesa sequestering solution that decreases the bonds in an implant, therefractive index of the resulting implant will be changed uponadministration of the sequestering solution. For example, an alginateand HA adhesion barrier is translucent when crosslinked, and transparentafter a calcium sequestering solution is applied. FIG. 1 shows anexample of membrane, 2 cm×4 cm, comprised of alginate and hyaluronate.The membrane is thin, flexible, hydrophilic, translucent, and has slick,lubricious surfaces.

In an embodiment, the hydrogel membrane and the sequestering solutionmay be provided within a kit. The kit would also include a deliverydevice suited for applying the sequestering solution to the wound site.A surgeon or other health care provider in an operating room settingwould use the kit to apply the membrane and appropriate volume ofsequestering solution to the wound site. This approach would afford theend user great flexibility to adjust the membrane size and solutionvolume to meet patient specific needs.

The sequestering solution may be applied to the membrane hours, days, orweeks after the membrane's implantation. For example, the hydrogelmembrane may be placed at a wound site (e.g., flexor tendon repair) forthe prevention of unwanted scar tissue attachments. After the timeperiod for scar formation has passed, generally 3 to 14 days, themembrane barrier is no longer needed; therefore, the sequesteringsolution may be injected into the wound site to completely solubilizethe membrane. This action would have as its purpose elimination of themembrane from the wound site thus precluding an unwanted foreign bodyresponse. The sequestering solution can be introduced by a needle andsyringe penetrating through the surrounding tissue or can be introducedby minimally invasive surgical means.

Multilayer Hydrogel

One embodiment of the invention includes a polysaccharide-based bilayerhydrogel film that promotes regeneration in one layer and preventsunwanted scar tissue formation in a second layer. Hydrogels, such asthose described in WO2009/108760, WO2012/048283, WO2012/048289, are usedto form a multi-layer hydrogel with distinct layers that provides aregenerative effect in one layer, and an anti-adhesive effect in asecond layer. The hydrogel regenerative layer promotes cell attachmentand proliferation in vitro. The hydrogel anti-adhesive layer preventsunwanted cell attachment and limits fibrotic tissue formation. Hydrogelscan be rolled into a conduit with either the anti-adhesive or theregenerative side exposed to the lumen.

An embodiment includes a bilayer hydrogel composed of biopolymers thatprevent scar tissue attachment on one side, and encourage healthyregeneration on the other side. The anti-adhesive layer is comprised ofhyaluronic acid and alginate. The regenerative layer is comprised ofcollagen and hyaluronic acid. The two layers are distinct and arecovalently bound. An embodiment includes a collagen matrix thatencourages cell attachment and proliferation.

Embodiments solve the problems of unwanted soft tissue attachments aswell as decreasing critical healing time by supporting regeneration ofinjured tissues. Various embodiments provide anti-adhesive andregenerative layers using nonsynthetic, all-natural components. Anembodiment includes a biocompatible, bilayer hydrogel composed ofnaturally occurring polysaccharides.

An embodiment is self-adherent and does not require sutures or screws.An embodiment may be coupled (e.g., coated with) a mesh material toallow for better tissue coupling (e.g., suturing tissue to the mesh) andmay be useful in various procedures such as hernia repair,cholecystectomy, and the like. More generally, embodiments may beimplanted in various surgeries including surgeries in the peritonealcavity and/or procedures relating to abdominal, gynecological, lung,tendon, cardiac, nerve anatomy and the like.

In one embodiment membranes of alginate and a photo-reactive derivativeof hyaluronic acid (GMHA) were prepared according to methods such asthose described in WO2009/108760, WO2012/048283, WO2012/048289, all ofwhich are hereby incorporated by reference. After preparation of thefirst membrane layer, the sample was dried under sterile conditions anda second layer of collagen and GMHA was cast on top. The two layers werechemically crosslinked and fused by treatment with1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC). Bilayer formationwas confirmed using confocal images of fluorescently labeled hyaluronicacid and immunostained collagen. In vitro cell morphology wascharacterized using diamidino-2-phenylindole (DAPI). In vitro cellmorphology and characterization indicate that the collagen layereffectively provides an adhesive, proliferative substrate. Theanti-adhesive layer effectively prevents cell proliferation andattachment.

FIG. 4 includes images of a bilayer film comprising alginate,hyaluronate, and collagen. This film was imaged by confocal laserscanning fluorescence microscopy. FIGS. 4(A) and 4(B) depict thepresence of fluorescently labeled hyaluronic acid in the anti-adhesivelayer (comprising hyaluronate and alginate) and the regenerative layer(comprising hyaluronate and collagen), respectively. FIG. 4(C) shows theadherent morphology of human dermal fibroblast cells attached to theregenerative layer. FIG. 4(D) shows the cells are poorly attached to theanti-adhesive layer. FIG. 4(E) is a photograph depicting theadvantageous handling properties of the bilayer film. Altogether, theseimages indicate that the regenerative layer provides an adhesivesubstrate for cells and the anti-adhesive layer effectively preventscellular attachment.

In FIG. 5 HA is a linear polysaccharide with repeating disaccharideunits composed of sodium D-glucuronate and N-acetyl-D-glucosamine. Thisnaturally occurring glycosaminoglycan is a component of skin, synovialfluid, and subcutaneous and interstitial tissues. HA is metabolicallyeliminated from the body, and plays a role in protecting and lubricatingcells and maintaining the structural integrity of tissues. Anioniccarboxylic groups immobilize water molecules giving HA its viscoelasticand anti cell-adhesive properties. In various embodiments, the layerscan be fused together using any suitable crosslinking technique. Forexample, photoinitiated crosslinking of the film's components, graftedwith polymerizable functionalities, will fuse the layers. Suitablechemical crosslinkers, such as EDC, may also be used. Ioniccrosslinking, such as calcium crosslinking of alginate components, canalso fuse together the various layers. One can see surgical field evenwith addition of second layer.

While FIG. 5 includes crystal templating another embodiment may involvethe same process however the embodiment omits crystal templating relatedsteps (e.g., steps 2 and 5 are not practiced in an embodiment but theremaining steps of FIG. 5 are practiced) and instead proceeds with anantiadhesive layer consisting essentially of HA and alginate.

While bilayer hydrogels have been repeatedly discussed embodiments arenot limited to two layers and may instead include 3, 4, 5, 6, 7, 8 ormore layers. Outer layers may both be anti-adhesive with one or moreproregenerative layers located between the outer layers.

Also, embodiments are not restricted to HA/collagen and alginate/HAlayers. For example, the anti-adhesive layer may be composed of anypolymer or combinations of polymers that present a lubriciousnon-adhesive surface. The regenerative layer may be composed of anycombination of polymer or protein (e.g., laminin) that promotes cellularattachment and proliferation.

Therapeutic Agent Delivery

An embodiment of the invention includes a biocompatible membranecomprised of alginate and hyaluronate that releases a pharmaceuticallyactive ingredient at a wound site. The active ingredient may be anantibiotic, anti-inflammatory, chemotherapeutic, anti-scarring, and/orproregenerative drug such as a growth factor or stem cell.

Scarring, inflammation, and bacterial infection are unwantedcomplications of surgical procedures. During a surgical procedure thetissues and organs of the body may be deliberately or inadvertentlyinjured. These injuries may prompt a wound healing response that resultsin scarring and inflammation. Scarring may be problematic when itproduces scar tissue attachments between adjacent tissues and organsthat should remain unattached. A patient may be prone to bacterialinfection particularly around polymeric or metal implants that provideniches for bacterial growth.

An embodiment includes a membrane, comprising alginate and hyaluronate,with an entrapped pharmaceutically active ingredient. An embodiment iscomprised essentially of alginate and hyaluronate, with an entrappedpharmaceutically active ingredient. In an embodiment a drug-loadedmembrane is obtained by mixing alginate and hyaluronate with the activeingredient, either in a dispersed or microcrystalline form, in solutionand then using a method, such as casting into a mold, spin-coating,doctor blading, and the like to obtain a planar membrane. The membranesmay then be stabilized through crosslinking with multivalent cations,such as calcium (but not limited to calcium). Optionally, the membranesmay be further stabilized by substituting either alginate or hyaluronatewith photo-reactive derivatives thereof that undergo chemicalcrosslinking when triggered by ultraviolet or visible light sources. Inan embodiment membranes may be prepared without the active ingredientand then subsequently loaded with the ingredient. For example, amembrane may be dipped into a concentrated solution thus allowing themembrane to absorb the active ingredient from the solution. In anembodiment the membrane may be incubated with a solution of an activeingredient that becomes covalently or electrostatically bound to thepolymers comprising the membrane.

An embodiment includes a method for using one of the aforementioneddrug-loaded membrane embodiments to inhibit, reduce, or preventscarring, inflammation, or bacterial infection. The membrane may be usedin any anatomical location of the body following a surgical procedurefor which there is a risk of unwanted scarring or inflammation. Forexample, the abdominal cavity, peritendinous space, sinus cavity, andthe like. Likewise, the membrane may be placed near or around anyimplant that poses a risk for bacterial infection. An embodimentincludes a method for using an aforementioned drug-loaded membraneembodiment to deliver a chemotherapeutic to a tumor or to a surgicalsite following tumor resection. In an embodiment the invention is amethod for using an aforementioned drug-loaded membrane embodiment todeliver pro-regenerative agents, such as growth factors and stem cells,to enhance tissue repair and healing. A membrane may be used in bothopen and minimally invasive surgical procedures.

An embodiment includes a method of treating a drug-loaded membrane witha stimulus, preferably a solution or gel, to modify the releaseproperties of the membrane. For example, the solution may increase therate of membrane dissolution thus increasing the rate of release of theentrapped pharmaceutically active ingredients. Such a solution includesa chelator that sequesters the multivalent cations stabilizing themembrane. In an embodiment a solution is comprised essentially of achelator that sequesters the multivalent cations stabilizing themembrane. The solution may be applied following placement of themembrane onto a wound or into a surgical site. However, in anotherembodiment the solution may be applied to the membrane hours, days, orweeks after the membrane's implantation. By applying the solution at alater point in time a medical care provider will be capable of tailoringthe drug release to match the particular needs of the patient.

An embodiment includes a membrane that targets release of the activeingredient to the wound site so the side-effects of systemic deliverycan be avoided. Such an embodiment is biocompatible and bioresorbable.Embodiments including membranes may be easily cut and trimmed during asurgical procedure and are convenient for covering the wounded surfacesof tissues and organs. Such embodiments may be inserted into a deep orsuperficial wound to release an active ingredient that will reduce orprevent scarring, inflammation, or bacterial infection.

The hydrogel membrane is comprised of a network of alginate andhyaluronate that is swelled in water. This network provides pores thatcan absorb an active ingredient from a concentrated solution. The poresof the hydrogel membrane comprise interconnected pathways through whichwater can permeate. Initially, the pores are small, in the range ofangstroms to nanometers, and can accommodate only small molecules suchas solvents, salts, and organic metabolites. Permeation of the membranewith water swells the pores thereby increasing their size and volume.The fully swelled pores, in the range of nanometers to micrometers, canaccommodate the diffusion of peptides, proteins, and macromolecules.

The pores of the membrane may also be formed by the leaching of themembrane's hyaluronate component. When the ratio of hyaluronate toalginate is low the hyaluronate component is entirely or partiallyentrapped within the crosslinked alginate matrix and leaching islimited; but when the ratio of hyaluronate to alginate is high, thecrosslinked alginate may be unable to retain the leachable hyaluronatecomponent. The hyaluronate component can be leached by rinsing themembrane in water for which hyaluronate has a strong affinity. Whenhyaluronate is leached it leaves behind empty pores within the membranethat provide an interconnected pathway for diffusion of water and drugmolecules. The leaching of hyaluronate from the membrane may occur invivo and be used as a method to deliver hyaluronate to a wound site.This may be advantageous as a method to capitalize on hyaluronate'spro-regenerative wound healing properties.

In an embodiment, the membranes can be prepared with an interconnectednetwork of pores, on the scale of micrometers to hundreds ofmicrometers, through crystal templating. Crystal templating is a methodin which nucleation and growth of crystals within a cast film creates aporous network. Such a membrane could be prepared by casting a solutionof alginate, hyaluronate, and a crystallizable molecule into a form orvessel; allowing the solvent to evaporate; growing crystals of thecrystallizable molecule through spontaneous nucleation or deliberateintroduction of a seed; crosslinking the alginate and/or hyaluronatearound the crystals; and dissolving the crystals such that a porenetwork in the shape of the crystals has been templated into themembrane. The process of crystal growth ensures the interconnectivity ofthe pores and can yield dendritic architectures. This pores-basedarchitecture has advantageous affects on the diffusion and release ofentrapped drug molecules (e.g., continuous pores allow for greaterdiffusion of drugs into the hydrogel).

Solutions from which the membranes may absorb drugs or other therapeuticagents may be aqueous solutions because water is a good solvent for bothswelling of the hydrogel membrane and facilitating the diffusion ofactive ingredient into the pores. However, many drugs have poorsolubility in water; therefore, the concentrated solutions may also bemixed solutions comprising water and a water-miscible solvent, such asan alcohol (e.g., methanol, ethanol, ethylene glycol, and the like), awater-miscible polar aprotic solvent (e.g., acetone, dimethyl sulfoxide,dimethylformamide, and the like), an acid, and/or base. These mixedsolutions have the benefit of both dissolving drugs that are poorlywater soluble and for swelling the membrane. The proportion of water inthese mixtures may range from 100% to 0% to suit the solubilityproperties of a particular drug.

The hydrogel membrane is not limited to the type of drug which it mayincorporate. In various embodiments the hydrogel membrane mayincorporate proteins, peptides, and small molecules. Embodiments mayinclude chemotherapeutics, pro-regenerative drugs such as growth factorsand stem cells, and drugs used for the prophylaxis or treatment ofinflammation, infection, scarring, and adhesion. Embodiments maycomprise an active ingredient selected from vancomycin, tobramycin,doxorubicin, mometasone furoate, and their hydrochloride salts. In anembodiment the hydrogel membrane may also be formulated to releasemacromolecules such as vascular endothelial growth factor and sodiumhyaluronate. The hydrogel membrane may be formulated with non-activeingredients, such as binders, surfactants, salts, and the like tosupport the release of the active ingredient.

The drug-loaded hydrogel membrane may be used during surgicalprocedures. In one embodiment the drug-loaded membrane may be placed ontop of wounded tissues and organs to reduce scarring and inflammation.The wounded tissues may be either internal, in which case the membranewould be inserted into a body cavity, or external, in which case themembrane would be applied topically over the wounded area. In anembodiment, the drug-loaded membrane may be placed adjacent to implantsthat are at risk for introducing a bacterial infection into the surgicalsite. In an embodiment, the drug-loaded membrane may be placed near atumor or at the site of a tumor resection to release a chemotherapeutic.

In an embodiment, the hydrogel membrane, initially unloaded with drug,may be provided within a kit that includes a drug component that is tobe combined with the membrane just prior to use. This approach may beadvantageous by allowing separate storage conditions for the membraneand drug. For example, a surgeon, nurse, or other health carepractitioner in a hospital, office, or operating room setting may openthe kit, dip the membrane into the drug solution, and then apply thedrug-soaked membrane to an injury site. This approach would afford theend user great flexibility to mix and match membrane and drugcombinations to meet patient specific needs based on disease state, bodyweight, age, and metabolism.

The timing of the release of drugs from the hydrogel membrane isdetermined by a number of factors. Among these factors are the amount ofdrug loaded, the membrane composition (e.g., ratio of hyaluronate toalginate), the extent of crosslinking, and the water content of themembrane. For example, increasing the ratio of hyaluronate to alginatemay decrease the crosslink density of the membrane thereby increasingthe permeability of the membrane to diffusion of encapsulated drug. Asanother example, membranes with greater water content may exhibit fasterrelease because water content through swelling is correlated to membraneporosity.

In an embodiment the release of active ingredient from the membrane maybe modified by the use of a stimulus. Such a stimulus, in the form of anaqueous solution or gel, comprises a chelator that sequesters thecrosslinking ions (e.g., calcium) that stabilize the membrane. In anembodiment such a stimulus, in the form of an aqueous solution or gel,may be comprised essentially of a chelator that sequesters thecrosslinking ions (e.g., calcium) that stabilize the membrane. Suitablechelators are salts of organic molecules that have multiple anionicfunctional groups capable of bonding to calcium (or whatevercrosslinking ion was used). Examples are the salts of citric acid, EDTA,EGTA, BAPTA, tetracycline, and phosphates. The stimulus may be appliedduring surgical procedures following insertion of the membrane into aperson's body. In response to the stimulus the membrane swells,increasing the pore size of the membrane, and increasing the rate ofdiffusion of active ingredient from the membrane into the woundenvironment. The pore size may be increased by at least a factor of 10and up to a factor of 1,000 or more. The beneficial effect of thestimulus is that the rate of drug release may be tailored to match apatient with respect to body weight, age, metabolism, or disease state.The stimulus may be delivered via syringe, spray mechanism, or the like,to the surface of the implanted membrane.

In another embodiment the stimulus may be applied to the membrane hours,days, or weeks after the membrane's implantation. For example, ahypothetical membrane loaded with vancomycin, an antibiotic, may beinserted adjacent to a bone implant. This membrane will exhibit arelease of antibiotic. If a health care provider recognizes symptoms ofinfection around the bone implant they may choose to stimulate themembrane to increase the release rate of this antibiotic to combat theinfection. After the entirety of drug has been released the health careprovider may decide that the membrane, having served its purpose ofvancomycin delivery, should be completely solubilized through the actionof the stimulus thus eliminating the presence of the foreign membranefrom the wound site. The stimulus can be introduced by a needle andsyringe penetrating through the surrounding tissue or can be introducedby minimally invasive surgical means.

Many of the aforementioned embodiments combine a therapeutic agent witha porous hydrogel. One such porous hydrogel mentioned concerned acrystal template hydrogel. As one example, the embodiments found in U.S.Pat. Appl. Pub. No. US20110008442 may be utilized with therapeutics. Theapplication, the contents of which are hereby incorporated within,includes some embodiments having hydrogels with pores formed via crystaltemplating and other embodiments having pores formed without crystaltemplating. The therapeutic agents described herein may be includedthese pores of any of these embodiments.

An embodiment includes a tissue anchor that may be used to deploytherapeutic agent. For example, a hydrogel including a therapeutic agentmay be applied to an agent. The hydrogel may be applied to the patientand left alone. However, a stimulus may be used to “tune” the hydrogel.For example, a hydrogel may include calcium crosslinking and atherapeutic agent. A calcium chelator may be applied to the calciumcrosslinked hydrogel to (1) help the hydrogel adhere to the patient(e.g., adhere to a tumor), (2) promote or tune the dissolution time forthe hydrogel (e.g., 1 hour or 1 week), and (3) tune the therapeuticagent application time (e.g., 1 hour or 2 weeks).

Embodiments may be combined with multilayer hydrogels described above.Thus, an embodiment includes a multilayer hydrogel that may be used todeploy therapeutic agent. The multilayer hydrogel may include a firstlayer that provides a regenerative effect (e.g., a regenerative layerincluding collagen and hyaluronic acid), and a second layer that isanti-adhesive (e.g., an anti-adhesive layer including hyaluronic acidand alginate) and further includes a therapeutic agent with the pores ofthe second layer.

An embodiment includes a film with four factors that may be beneficialfor an adhesion barrier. Embodiments solve a traditional burden withadhesion barriers—poor handling characteristics. This has preventedstrong market acceptance of barriers. Regarding the four factors, thefirst factor includes the ability for the barrier to be manipulated inways relevant to a surgical setting (e.g., open surgery, using a trocarfor laparoscopic delivery, and the like). The second attribute is tissueadherence. If the barrier can remain in place where it is implanted,then it not only provides a site specific tissue support but alsoeliminates (or at least reduces) the requirement for sutures or anotherfixing step. The third attribute is conformability. The last attributeis bioresorbability. An embodiment of the invention meets all four ofthese factors.

An embodiment uses a technique for adding porosity and fibers to ahydrogel. There is flexibility to use different crystals, differentdensities of biopolymer to make for a process that is easily adjustable,gives different polymer properties, different patterns, and the like. Inaddition to this flexibility is the ability to scale up production ofthe hydrogels. An embodiment includes photocrosslinking HA around thecrystalline network and then further chemically crosslinking thealginate around the crystalline network. Compression of the biopolymersinto fiber-like structures reinforces the strength of the film while theporous network gives rise to elasticity. Thus, the crystallizationprocess imparts unique fibers and pores that provide required handlingproperties in otherwise brittle materials. The crystallization processis inexpensive, simple, not time consuming, and does not requiresophisticated equipment or skills. Film casting is not different fromany other casting.

An embodiment may be applied wet, which lends itself to endoscopicprocedures and removes the need to dessicate the surgical field. Thefilm is flexible and is translucent to allow a view of the surgicalfield. Also, a surgical incision can be much smaller than the wettedimplant. An embodiment of the film is also repositionable for a time.For example, with one embodiment upon initial placement within thesurgical field the films are easily repositionable. However, within 24hours of placement the films undergo a gel-to-mucinous transformation.At this point the films are no longer repositionable and are stronglyadhered to the tissue. This transformation is caused by displacement ofcalcium crosslinks within the films by endogenous sodium ions.

An embodiment of the invention includes a membrane comprising alginateand hyaluronate. The membrane can be obtained by methods such as castinginto a mold, spin-coating, doctor blading, extrusion, and the like. Themembranes are stabilized through crosslinking with multivalent cations,preferably calcium. Optionally, the membranes can be further stabilizedby substituting either alginate or hyaluronate with photo-reactivederivatives thereof that undergo chemical crosslinking when triggered byultraviolet or visible light sources.

An embodiment of the invention is a method for using the aforementionedmembrane to inhibit, reduce, or prevent scar tissue attachments. Themembrane may be used in any anatomical location of the body for whichthere is a risk of scar tissue attachments. During a surgical procedurethe membrane may be placed between two apposing organs or tissues. Themembrane may be used in both open and minimally invasive surgicalprocedures.

An embodiment of the invention is a method of treating theaforementioned membrane with a stimulus, preferably a solution or gel,to modify the properties of the membrane. For example, the solution mayenhance the tissue adherence of the membrane or increase the rate ofmembrane resorption within the body. Such a solution comprises achelator (e.g., calcium chelator) that binds the multivalent cationsstabilizing the membrane. The solution is applied during surgicalprocedures following insertion of the membrane into a person's body.Optionally, the solution may also comprise viscosity modifiers tofacilitate surgical delivery.

An embodiment of the invention is the aforementioned membrane,comprising alginate and hyaluronate, with an entrapped pharmaceuticallyactive ingredient. The active ingredient may be an antibiotic,anti-inflammatory, chemotherapeutic, anti-scarring, and/orpro-regenerative drug such as a growth factor or stem cell. In anembodiment the release of active ingredient from the membrane may bemodified by the use of the aforementioned stimulus.

An embodiment of the invention is a bilayer hydrogel membrane comprisingtwo distinct layers of which one inhibits, reduces, or prevents scartissue attachments and the other layer promotes wound healing andregeneration. The two layers are joined through chemical, ionic, orphysical bonds.

The following examples pertain to further embodiments.

Example 1 includes uncrosslinked hyaluronic acid and crosslinkedalginate both included in a hydrogel film; and a calcium chelator;wherein (a) the alginate is crosslinked with calcium, (b) the hydrogelfilm is flat and includes a width, a length, and a thickness that isless than the width and the length, and (c) the hydrogel film isconfigured so bioresorbability of the hydrogel film increases inresponse to applying the calcium chelator to the hydrogel film.

In example 2 the subject matter of the Example 1 can optionally includewherein the calcium chelator is configured to disrupt calcium crosslinkswithin the hydrogel film.

In example 3 the subject matter of the Examples 1-2 can optionallyinclude wherein the calcium chelator is selected from the groupcomprising citrate, EDTA, EGTA, and BAPTA.

In example 4 the subject matter of the Examples 1-3 can optionallyinclude wherein concentration of the calcium chelator is 0.05 to 1.0molar.

In example 5 the subject matter of the Examples 1-4 can optionallyinclude a thickening agent.

In example 6 the subject matter of the Examples 1-5 can optionallyinclude wherein the thickening agent includes sodium hyaluronate.

In example 7 the subject matter of the Examples 1-6 can optionallyinclude wherein the thickening agent is configured to increase viscosityof the calcium chelator.

In example 8 the subject matter of the Examples 1-7 can optionallyinclude wherein the hydrogel film consists essentially of hyaluronicacid and alginate.

In example 9 the subject matter of the Examples 1-8 can optionallyinclude wherein the hydrogel film comprises at least 1% and no more than33% composition hyaluronic acid.

In example 10 the subject matter of the Examples 1-9 can optionallyinclude a first hydrogel layer comprising the uncrosslinked hyaluronicacid and the crosslinked alginate; and

a second hydrogel layer comprising collagen and hyaluronic acid.

In example 11 the subject matter of the Examples 1-10 can optionallyinclude wherein the first hydrogel layer is monolithic, the secondhydrogel layer is monolithic but not monolithic with the first hydrogellayer, and the first and second hydrogel layers are covalently bound toone another.

In example 12 the subject matter of the Examples 1-11 can optionallyinclude a third hydrogel layer comprising additional uncrosslinkedhyaluronic acid and additional crosslinked alginate;

wherein the third hydrogel layer is monolithic but not monolithic withthe second hydrogel layer, the third and second hydrogel layers arecovalently bound to one another, and the second hydrogel layer isbetween the first and third hydrogel layers.

In example 13 the subject matter of the Examples 1-12 can optionallyinclude wherein the alginate is crosslinked around the uncrosslinkedhyaluronic acid.

In example 14 the subject matter of the Examples 1-13 can optionallyinclude wherein the hydrogel film comprises a therapeutic agent selectedfrom the group comprising a drug, a pharmaceutical agent, a peptide, aprotein, a medicine, a hormone, and a macromolecule.

In example 15 the subject matter of the Examples 1-14 can optionallyinclude wherein the hydrogel film is configured so the hydrogel film'srelease rate for the therapeutic agent increases in response to applyingthe calcium chelator to the hydrogel film.

In example 16 the subject matter of the Examples 1-15 can optionallyinclude wherein the alginate is crosslinked around the therapeuticagent.

In example 17 the subject matter of the Examples 1-16 can optionallyinclude wherein the hydrogel film is configured so the hydrogel film'srelease rate for the therapeutic agent increases in response toincreasing the amount of hyaluronate in the hydrogel film.

In example 18 the subject matter of the Examples 1-17 can optionallyinclude a therapeutic agent selected from the group comprising a drug, apharmaceutical agent, a peptide, a protein, a medicine, a hormone, and amacromolecule.

In example 19 the subject matter of the Examples 1-18 can optionallyinclude wherein the hydrogel film is configured so mucoadhesiveness forthe hydrogel film increases in response to applying the calcium chelatorto the hydrogel film.

In example 20 the subject matter of the Examples 1-19 can optionallyinclude wherein the hydrogel film is configured to increase intransparency in response to applying the calcium chelator to thehydrogel film.

In another embodiment the hydrogel film has a thickness of between 5 and30 micrometers. However, in other embodiments the thickness is nogreater than 5, 10, 15, 20, 25, 35, 40, 45, or 50 micrometers. In otherembodiments the hydrogel film has a thickness of between 5 and 10, 10and 15, 15 and 20, 20 and 25, 25 and 30, 30 and 40, 50 and 60, 70 and80, 90 and 100 micrometers. In another embodiment the hydrogel film hasa thickness not greater than 250 micrometers.

Example 21 includes a kit comprising: a hydrogel film consistingessentially of crosslinked alginate that is crosslinked arounduncrosslinked hyaluronic acid to entrap the uncrosslinked hylalunonicacid within the crosslinked alginate; and a sequestering agent; wherein(a) the alginate is crosslinked with an ion, (b) the hydrogel film isplanar, (c) the hydrogel film is configured so its bioresorbabilityincreases in response to applying the sequestering agent to the hydrogelfilm, and (d) the sequestering agent is configured to sequester the ion.

In example 22 the subject matter of the Example 21 can optionallywherein the hydrogel film comprises: a first hydrogel layer comprisingthe uncrosslinked hyaluronic acid and the crosslinked alginate; and asecond hydrogel layer comprising a therapeutic agent selected from thegroup comprising a drug, a pharmaceutical agent, a peptide, a protein, amedicine, a hormone, and a macromolecule; wherein (a) the first hydrogellayer is monolithic, (b) the second hydrogel layer is monolithic but notmonolithic with the first hydrogel layer, (c) the first and secondhydrogel layers are chemically bound to one another, (d) the secondhydrogel layer is adhesive, and (e) the first hydrogel layer isanti-adhesive.

In example 23 the subject matter of the Examples 21-22 can optionallyinclude wherein the hydrogel film includes a therapeutic agent selectedfrom the group comprising a drug, a pharmaceutical agent, a peptide, aprotein, a medicine, a hormone, and a macromolecule; and the hydrogelfilm is configured so its release rate for the therapeutic agentincreases in response to applying the sequestering agent to the hydrogelfilm.

In example 24 the subject matter of the Examples 21-23 can optionallyinclude wherein the hydrogel film is configured so mucoadhesiveness forthe hydrogel film increases in response to applying the sequesteringagent to the hydrogel film.

FIG. 6 includes a method in an embodiment.

Block 605 includes applying a hydrogel film to a subject, wherein thehydrogel film includes uncrosslinked hyaluronic acid and crosslinkedalginate, and the alginate is crosslinked with calcium.

Block 610 includes applying a calcium chelator to the hydrogel to (a)increase bioresorbability of the hydrogel film in response to applyingthe calcium chelator to the hydrogel film, (b) tune the hydrogel film'srelease rate for a therapeutic agent included in the hydrogel byapplying the calcium chelator to the hydrogel film, and/or (c)increasing the mucoadhesiveness for the hydrogel film by applying thecalcium chelator to the hydrogel film. Block 610 may occur once orrepeatedly. For example, the chelator may be added immediately after thehydrogel is applied to the patient. In addition, the chelator may beadded again several hours, days, or weeks after the initial chelatorapplication. In addition, the initial chelator application may occurhours, days, or weeks after the hydrogel is applied to the patient.

Block 607 is optional. Block 607 includes applying a thickening agent tothe calcium chelator to increase viscosity of the calcium chelator. Thismay be done before or after the calcium chelator is applied to thehydrogel.

In an embodiment the hydrogel film includes a first hydrogel layercomprising the uncrosslinked hyaluronic acid and the crosslinkedalginate; and a second hydrogel layer comprising collagen and hyaluronicacid. With such an embodiment block 605 may include applying the secondhydrogel layer to a wound of the patient.

In an embodiment the calcium chelator addressed in FIG. 6 is replacedwith sequestering agent and the calcium crosslinked is more generallybased on crosslinking based on an ion corresponding to the sequesteringagent.

Another embodiment includes a method comprising applying a hydrogel filmto a subject, wherein the hydrogel film includes uncrosslinkedhyaluronic acid and crosslinked alginate. The alginate is crosslinkedwith calcium, and the hydrogel film is flat and includes a width, alength, and a thickness that is less than the width and the length. Themethod further comprises applying a calcium chelator to the hydrogel toincrease bioresorbability of the hydrogel film in response to applyingthe calcium chelator to the hydrogel film. The method further comprisesapplying a calcium chelator to the hydrogel more than 1 day afterapplying the hydrogel to the patient. In an embodiment the methodfurther comprises applying a thickening agent to the calcium chelator toincrease viscosity of the calcium chelator. In an embodiment thehydrogel film includes a first hydrogel layer comprising theuncrosslinked hyaluronic acid and the crosslinked alginate; and a secondhydrogel layer comprising collagen and hyaluronic acid. The methodfurther comprises applying second hydrogel layer to a wound of thepatient. Another embodiment includes rolling the hydrogel film into aroll whose outer surface includes the first hydrogel layer. Theembodiment includes contacting the first hydrogel layer with trocar,introducer, or tube to introduce the hydrogel film into the patientwithout having the hydrogel film stick or adhere to the trocar,introducer, or tube. In an embodiment the hydrogel film comprises atherapeutic agent selected from the group comprising a drug, apharmaceutical agent, a peptide, a protein, a medicine, a hormone, and amacromolecule. The method may comprise tuning the hydrogel film'srelease rate for the therapeutic agent by applying the calcium chelatorto the hydrogel film. In an embodiment the method may compriseincreasing the mucoadhesiveness for the hydrogel film by applying thecalcium chelator to the hydrogel film.

Another embodiment includes a method comprising applying a hydrogel filmto a subject, wherein the hydrogel film includes uncrosslinkedhyaluronic acid and crosslinked alginate. The alginate is crosslinkedwith an ion, and the hydrogel film is flat and includes a width, alength, and a thickness that is less than the width and the length. Themethod further comprises applying a sequestering agent to the hydrogelto increase bioresorbability of the hydrogel film in response toapplying the sequestering agent to the hydrogel film. In an embodimentthe method further comprises applying a thickening agent to thesequestering agent to increase viscosity of the sequestering agent. Inan embodiment the hydrogel film includes a first hydrogel layercomprising the uncrosslinked hyaluronic acid and the crosslinkedalginate; and a second hydrogel layer a therapeutic agent. The methodfurther comprises applying second hydrogel layer to a wound of thepatient. Another embodiment includes rolling the hydrogel film into aroll whose outer surface includes the first hydrogel layer. Theembodiment includes contacting the first hydrogel layer with trocar,introducer, or tube to introduce the hydrogel film into the patientwithout having the hydrogel film stick or adhere to the trocar,introducer, or tube. In an embodiment the hydrogel film comprises atherapeutic agent selected from the group comprising a drug, apharmaceutical agent, a peptide, a protein, a medicine, a hormone, and amacromolecule. The method may comprise tuning the hydrogel film'srelease rate for the therapeutic agent by applying the sequesteringagent to the hydrogel film. In an embodiment the method may compriseincreasing the mucoadhesiveness for the hydrogel film by applying thesequestering agent to the hydrogel film.

Another embodiment includes no kit but instead just includes a hydrogel.Such an embodiment includes uncrosslinked hyaluronic acid andcrosslinked alginate both included in a hydrogel film; wherein (a) thealginate is crosslinked with calcium, (b) the hydrogel film is flat andincludes a width, a length, and a thickness that is less than the widthand the length, and (c) the hydrogel film is configured sobioresorbability of the hydrogel film increases in response to applyinga calcium chelator to the hydrogel film. Such a calcium chelator wouldbe configured to disrupt calcium crosslinks within the hydrogel film. Inan embodiment the hydrogel film consists essentially of hyaluronic acidand alginate. In an embodiment the hydrogel film comprises at least 1%and no more than 33% composition hyaluronic acid. In an embodiment thehydrogel film comprises: a first hydrogel layer comprising theuncrosslinked hyaluronic acid and the crosslinked alginate; and a secondhydrogel layer comprising collagen and hyaluronic acid. In an embodimentthe first hydrogel layer is monolithic, the second hydrogel layer ismonolithic but not monolithic with the first hydrogel layer, and thefirst and second hydrogel layers are covalently bound to one another. Inan embodiment the hydrogel film comprises: a third hydrogel layercomprising additional uncrosslinked hyaluronic acid and additionalcrosslinked alginate; wherein the third hydrogel layer is monolithic butnot monolithic with the second hydrogel layer, the third and secondhydrogel layers are covalently bound to one another, and the secondhydrogel layer is between the first and third hydrogel layers. In anembodiment the alginate is crosslinked around the uncrosslinkedhyaluronic acid. In an embodiment the hydrogel film comprises atherapeutic agent selected from the group comprising a drug, apharmaceutical agent, a peptide, a protein, a medicine, a hormone, and amacromolecule. In an embodiment the hydrogel film is configured so thehydrogel film's release rate for the therapeutic agent increases inresponse to applying the calcium chelator to the hydrogel film. In anembodiment the alginate is crosslinked around the therapeutic agent. Inan embodiment the hydrogel film is configured so the hydrogel film'srelease rate for the therapeutic agent increases in response toincreasing the amount of hyaluronate in the hydrogel film. In anembodiment the hydrogel film is configured so mucoadhesiveness for thehydrogel film increases in response to applying the calcium chelator tothe hydrogel film. In an embodiment the hydrogel film is configured toincrease in transparency in response to applying the calcium chelator tothe hydrogel film. In an embodiment the hydrogel film has a thickness ofbetween 5 and 30 micrometers. In an embodiment the calcium chelatoraddressed in this paragraph is replaced with sequestering agent and thecalcium crosslinked is more generally based on crosslinking based on anion corresponding to the sequestering agent.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

What is claimed is:
 1. A kit comprising: uncrosslinked hyaluronic acidand crosslinked alginate both included in a hydrogel film; and a calciumchelator; wherein (a) the alginate is crosslinked with calcium, (b) thehydrogel film is flat and includes a width, a length, and a thicknessthat is less than the width and the length, and (c) the hydrogel film isconfigured so bioresorbability of the hydrogel film increases inresponse to applying the calcium chelator to the hydrogel film.